CryoEM Structure and Assembly Mechanism of a Bacterial Virus Genome Gatekeeper

Igor Orlov (1, 2) , Stephane Roche (3) , Sandrine Brasilès (3) , Natalya Lukoyanova (4) , Marie-Christine Vaney (5) , Paulo Tavares (3) , Elena V. Orlova (6, 4)

1 Inserm U964 - CNRS UMR7104 - IGBMC - Centre for Integrative Biology - CBI
2 University of Glasgow
3 I2BC - Institut de Biologie Intégrative de la Cellule
4 Birkbeck College [University of London]
5 Virologie Structurale - Structural Virology
6 UCL - University College of London [London]

Numerous viruses package their dsDNA genome into preformed capsids through a portal gatekeeper that is subsequently closed. We report the structure of the DNA gatekeeper complex of bacteriophage SPP1 (gp612gp1512gp166) in the post-DNA packaging state at 2.7 Å resolution obtained by single particle cryo-electron microscopy. Comparison of the native SPP1 complex with assembly-naïve structures of individual components uncovered the complex program of conformational changes leading to its assembly. After DNA packaging, gp15 binds via its C-terminus to the gp6 oligomer positioning gp15 subunits for oligomerization. Gp15 refolds its inner loops creating an intersubunit β-barrel that establishes different types of contacts with six gp16 subunits. Gp16 binding and oligomerization is accompanied by folding of helices that close the portal channel to keep the viral genome inside the capsid. This mechanism of assembly has broad functional and evolutionary implications for viruses of the prokaryotic tailed viruses-herpesviruses lineage.

Mots clés: Bacteriophages; Electron microscopy; Phage biology; Viral proteins

Domaines: Biologie structurale [q-bio.BM]; Virologie

Igor Orlov, Stephane Roche, Sandrine Brasilès, Natalya Lukoyanova, Marie-Christine Vaney, et al.. CryoEM Structure and Assembly Mechanism of a Bacterial Virus Genome Gatekeeper. Nature Communications, 2022, 13 (1), pp.7283. ⟨10.1038/s41467-022-34999-8⟩. ⟨hal-03857097v2⟩